WO2013076235A1

WO2013076235A1 - Mould comprising a cavity for moulding a closing‑off device in a groove

Info

Publication number: WO2013076235A1
Application number: PCT/EP2012/073437
Authority: WO
Inventors: Wilfried CHADES; Richard BARRIERE; Bernard Villeneuve
Original assignee: Compagnie Generale Des Etablissements Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2011-11-25
Filing date: 2012-11-23
Publication date: 2013-05-30
Also published as: JP2015502275A; CN103946002B; JP6054411B2; EP2782733A1; US9616597B2; FR2983114A1; FR2983114B1; EP2782733B1; CN103946002A; US20140305565A1

Abstract

The invention relates to a moulding element for a mould for vulcanizing a tyre tread. This moulding element (1) comprises a base (3) able to mould a part of the tread surface of the tread and a rib (5) able to mould a groove in the tread. The rib has two longitudinal faces (11) extending in the lengthwise direction of this rib and protruding from the base and an upper face (9) connecting the longitudinal faces. The moulding element has a contact edge (17) formed by the base and the rib. This contact edge is intended to come into contact with another moulding element to form all or part of the vulcanizing mould. The moulding element further comprises at least one indentation (15) in the rib. This indentation opens onto the upper face (9) of the rib and onto the contact edge (17) of the moulding element. This indentation does not open onto the longitudinal faces (11) of the rib.

Description

MOLD COMPRISING A CAVITY FOR MOLDING A CLOSURE DEVICE IN A GROOVE

FIELD OF THE INVENTION

[01] The present invention relates to the field of manufacturing a tire mold having a plurality of cavities adapted to mold closure devices in one or more grooves (s) of this tire. More particularly, the invention relates to the manufacture of a mold formed from a plurality of molding elements.

STATE OF THE ART

[02] It is known from WO 2010146180 a tire vulcanizing mold comprising a plurality of molding elements. Each molding element is delimited by two edges of contact with two other adjacent molding elements so that once the molding elements in contact with each other, all of these molding elements allows the molding of all or part of the band of the tire.

[03] Each molding element comprises a base and a bead protruding from this base. The base is intended to mold the tread surface of the tread of the tire and the cord is intended to mold a groove in the tread of this tire, that is to say a cutout whose width is greater or equal to 2 mm.

[04] It is known that in the area of contact of the tread with the roadway, each groove forms with this roadway a resonance pipe. This resonance tube amplifies the rolling noise of the tire, which can be unpleasant for people inside the vehicle and / or outside of the vehicle.

[05] In order to limit the intensity of these resonance noises, it is known to provide the grooves with particular closure devices, also called "Flexible walls", "flaps" or "flaps". These closure devices are in the form of thin blades. These blades partially close the cross section of the grooves when the tire rolls on a dry pavement. In the case of driving on a wet pavement, the blades bend under the action of the flow of water, so that the evacuation of this water out of the contact zone of the tire with the roadway is possible. The adhesion of the tire on the road is then maintained even when driving under severe conditions of humidity. Such an example of a closure device is in particular known from WO 2010063749. [06] For molding these closure devices, the WO document

2010146180 discloses a molding element comprising a cord provided with housings adapted to receive inserts, each insert having a mold cavity of a closure device. The cord of the molding element is therefore discontinuous because interspersed with the housing receiving the inserts. [07] For certain types of tires such as tires for winter driving, it is known to provide the tread with incisions. Incision means a cutout whose width is less than 2 mm. These incisions are molded by lamellae protruding from the base of the molding element. In order to improve the mechanical strength of these strips, it is generally expected that they are integral with the bead of the molding element, that is to say that the strips and the bead are made at the same time during the same molding operation. But the inserts are manufactured during a step which is different from the step of molding the lamellae and the cord. Thus, in the case where it is desired to place lamellae at the level of inserts, for example due to a particular design of the tread, it is necessary to resort to an additional step of welding these lamellae with the inserts. This then leads to additional manufacturing costs.

[08] The invention therefore aims to improve the overall strength of a mold formed of several molding elements and having closure molds of molding cavities, while optimizing the manufacturing costs of this mold. DEFINITIONS

[09] "Pneumatic" means all types of elastic bandages subjected to internal pressure or not. [10] "Tread" of a tire means a quantity of rubber material delimited by side surfaces and by two major surfaces, one of which is intended to come into contact with a roadway when the tire is rolling.

[11] "Running surface" means the area formed by the points in the tread of the tire that come into contact with the road surface when the tire is rolling.

[12] "Mold" means a set of separate molding elements which, by relative approximation, to delimit a toroidal molding space.

[13] "Molding element" means a part of a mold. A molding element is for example a mold segment.

[14] By "base" is meant that part of the molding element having a molding surface capable of molding the tread surface of the tread of the tire. The base comprises in particular fixing means for fixing the molding element to the rest of the mold. [15] "Cord" means a protuberance protruding from the base and whose width is greater than or equal to 2 mm. The bead is intended to mold a groove in the tread of the tire.

[16] "Cavity" in a mold means a volume of hollow defined by walls of the mold. This cavity is able to mold a closure device in a groove molded by a cord.

[17] By "recess" in a cord ("recess" in English) means a hollow in the cord opening on a contact edge of the molding element. This recess is able to be closed at the contact edge of this molding element by another molding element to form a cavity. [18] By "contact edge" of a molding element is meant a surface of the molding element intended to come into contact with another molding element to form all or part of a vulcanization mold.

SUMMARY OF THE INVENTION

[19] The invention relates to a molding element for a mold for vulcanizing a tread of a tire. This molding element comprises a base capable of molding a portion of the tread surface of the tread and a bead capable of molding a groove in the tread. The cord comprises two longitudinal faces extending in the length of the cord protruding from the base and an upper face connecting the longitudinal faces. The molding element has a contact edge formed by the base and the cord. This contact edge is intended to come into contact with another molding element to form all or part of the vulcanization mold. The molding element has at least one recess in the bead. This recess opens on the upper face of the cord and on the contact edge of the molding element. This recess does not open on the longitudinal sides of the cord.

[20] The recess formed in the molding element is intended to be closed by another molding element of the mold to form a mold cavity of a closure device. The invention thus makes it possible to form these molding cavities in a simple and practical manner.

[21] In addition, since the recess formed in the molding element does not open at the longitudinal walls of the cord, this cord is not discontinuous. Thus, it is possible to mold slats integrally with the cord and this regardless of the positions of these slats relative to the cord.

[22] Finally, since the recess of the molding element opens on the edge of this molding element, the walls of the molding element delimiting this recess are easily accessible, especially before the assembly of this molding element in the mold. . Thus, it is possible to coat these walls with a non-stick coating, such as xylan. By the use of this anti-adhesive coating, the release of the closure devices is improved.

[23] In an alternative embodiment, the molding element comprises in the cord a first recess and a second recess, each of these recesses opening on the upper face of the cord and on the contact edge of the molding element, none of these recesses do not lead to the longitudinal faces of this cord.

[24] It is thus possible to mold in the same groove two closure devices belonging to the same transverse plane, these two closure devices being fixed in the bottom of the groove. This is particularly useful when the groove has a large width, for example a width greater than 15 mm. Indeed, two closing devices each closing half the width of the groove generally have greater flexibility with respect to a single device extending over the entire width of this groove. These two closure devices then have a good ability to flex when driving on a wet pavement. This optimizes the evacuation of water out of the contact zone of the tread with the roadway.

[25] In an alternative embodiment, the molding element comprises an air outlet channel, said evacuation channel extending the recess or each recess throughout the thickness of the base.

[26] This ensures a good evacuation of air trapped in the recess or recesses during vulcanization of the tire.

[27] In an alternative embodiment, the molding element comprises means for adjusting the dimensions of the exhaust duct.

[28] This ensures that the air is well evacuated during the vulcanization of the tire while preventing an escape of the rubber by the channel discharge. This prevents a surplus of rubber molded by the evacuation channel to form on the upper part of the closure device. Indeed, such a surplus of rubber could adversely affect the proper functioning of this closure device.

[29] In an alternative embodiment, the molding element comprises means for adjusting the height of the recess or each recess in the cord.

[30] When the tire is cooled once it is molded, the closing device may retract, changing its height in the groove of the tire. The importance of this retraction phenomenon is difficult to quantify. Indeed, this phenomenon depends on many factors such as the volume of gum forming the closure device, the temperature conditions of the vulcanization, the gum composition used. In order to give the tire a uniform appearance when it is in the new condition, it is advantageous to have the upper part of the closure device flush with the tread surface of the tread. By providing means for adjusting the height of the recess, it is possible to obtain, by successive tests, a closure device with the height which is suitable to ensure a uniform appearance of the tire.

[31] Another object of the invention is a mold for vulcanizing a tread of a tire. This mold comprises a plurality of molding elements. These molding elements are in contact with each other to form a molding surface capable of molding a tread surface of the tread of the tire. These molding elements also form at least one bead capable of molding a groove in the tread. This cord has two longitudinal faces extending in the length of the bead protruding from the molding surface and an upper face connecting these longitudinal faces. The mold object of the invention is remarkable in that it comprises at least one cavity capable of molding a closure device intended to close all or part of a cross section of the groove molded by the cord. This cavity opens on the face upper cord and does not open on the longitudinal sides of this cord so that the closure device molded by the cavity is integral with the material of the bottom of the groove. In addition, the cavity is delimited by walls belonging to two molding elements in contact with each other and at least one of said molding elements conforms to a molding element as described above.

[32] It is thus possible to manufacture in a simple and practical manner a mold capable of molding closure devices in the tread of a tire.

[33] In an alternative embodiment, the cavity is formed by two recesses vis-à-vis, each recess belonging respectively to one of the two molding elements in contact with each other.

[34] It is thus possible to manufacture a cavity by bringing together two recesses belonging to two different molding elements. Each recess can be formed during a stamping operation, that is to say by deformation of the material. As the depth of each recess is limited, there is therefore less material to deform, the stamping operation is then simplified.

[35] In an alternative embodiment, the cavity comprises a single recess belonging to one of the two molding elements. This cavity is formed by the recess and by a contact edge belonging to the other molding element. This contact edge then closes the recess.

[36] Thus, it is not necessary that the other molding member closing the recess also includes a recess. It is therefore possible to use standard molding elements having no recess in the manufacture of the mold. This limits the manufacturing costs of this mold.

[37] In an alternative embodiment, the width of the cavity is between 0.1 mm and 2 mm. [38] It is thus possible to mold thin closing devices. This small thickness of the closing devices gives them a good bending capacity when driving on a wet pavement.

Another object of the invention relates to a tread of a tire molded and vulcanized from the mold as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[40] Other features and advantages of the invention will emerge from the following description, given by way of example, without limitation, with reference to the accompanying drawings, in which: FIG. 1 schematically represents a partial perspective view of a molding element according to a first embodiment of the invention; Figure 2 schematically shows a sectional view of the molding element of Figure 1; Figure 3 schematically shows a sectional view of a molding element according to a second embodiment of the invention; Figure 4 schematically shows a sectional view of a molding element according to the third embodiment of the invention; Figure 5 schematically shows a sectional view of a molding element according to a fourth embodiment of the invention; Figure 6 shows a molding cavity formed from two recesses, each of these recesses respectively belonging to a molding element; Fig. 7 shows a molding cavity formed from a single recess; Figure 8 shows schematically a perspective view of a molding element according to a fifth embodiment of the invention; Figure 9 schematically shows a perspective view of a molding element according to a sixth embodiment of the invention.

[41] In the description which follows, substantially identical or similar elements will be designated by identical references.

[42] Figure 1 schematically shows a perspective view of a molding element 1 of a mold according to a first embodiment of the invention. To facilitate the understanding of the invention, no lamellae for molding an incision have been shown in this FIG.

[43] The molding element 1 comprises a base 3 and a bead 5 protruding from said base 3. The base 3 and the bead 5 are here made of material and are formed of an aluminum-type material.

[44] More particularly, the base 3 comprises a molding surface 7 for molding a portion of the running surface of a tire. The cord 5 comprises an upper face 9 for molding the bottom of a groove and two longitudinal faces 11, only one of which is shown here. These longitudinal faces 11 protrude from the molding surface 7 of the base 3.

[45] To facilitate understanding of the invention, the cord 5 has been shown here as generally forming a rectangular parallelepiped. Of course the invention is not limited to this particular form of the cord. Alternatively, the upper face 9 of the cord may be non-flat, for example curved, so that the bottom of the groove molded by the upper face of the cord 5 is curved. In the same way, the angle formed by the longitudinal faces 1 1 with the molding surface 7 of the base 3 may be different from 90 °. For example, each longitudinal face may form an angle greater than 0 ° and less than or equal to 45 ° with a direction normal to In addition, the upper face of the cord may comprise connecting portions with the longitudinal faces 11. These connecting portions are for example curvilinear so that it is possible to limit the presence of right angles between the bottom of the groove molded by the upper face of the cord and the longitudinal walls of this groove. This limits the risk of cracks appearing in the groove.

[46] In more detail, the cord 5 has two protuberances

13 delimiting a recess 15. This recess is intended to receive raw gum for molding a closure device in a groove of a tire. The protuberances 13 are here arranged so that the recess 15 does not open on the longitudinal faces 1 1 of the cord 5. On the other hand, the arrangement of these protuberances 13 allows the recess 15 to open at the same time on the upper face 9 of the cord 5 and on a contact edge 17 of the molding element 1.

[47] Figure 2 shows in more detail the recess 15. The recess 15 is thus delimited by a transverse wall 19, by two longitudinal walls 21, only one of which is here represented, and by a bottom wall 23. The wall transversely 19 is here perpendicular to the two longitudinal walls 21. Alternatively, it is possible that the transverse wall 19 forms an angle different from 90 ° with each of these longitudinal walls 21.

[48] It will also be noted that the depth P of the recess 15, that is to say the dimension of this recess in the length of the bead, is here constant and is between 0.1 mm and 1 mm. As a variant, the depth of the recess 15 may vary in the height H of this recess 15. This is possible in particular when the transverse wall 19 forms an angle other than 0 ° with a direction normal to the bottom wall 23.

[49] Figure 3 shows an alternative embodiment in which is added on the bottom surface 23 a shim 25. This shim 25 has a thickness corresponding to the width of the bottom surface 23 and has a height determined according to the desired height of the closure device molded by the recess 15. The adjustment wedge 25 may be formed of the same material as the molding element and is fixed to this molding element by gluing, screwing or any other means.

[50] Figure 4 shows another alternative embodiment in which the recess 15 is extended throughout the thickness of the base 3 by an exhaust duct 27. Thus, this exhaust channel 27 opens on an outer surface 29 of the base. This outer surface 29 is adapted to be in contact with the air during use of the molding element, and more particularly when the mold is closed during the vulcanization step. It will be noted that the depth of the discharge channel 27 is of the order of 0.03 mm. It will also be noted that this channel 27 is here represented as being opening on the contact edge 17 of the molding element. Alternatively, the discharge channel 27 may be entirely delimited by the base 3 and not lead to the contact edge of the molding element.

[51] Preferably, the section of the evacuation channel 27 is partially closed by an obstruction wedge 31, as can be seen in FIG. 5. This obstruction wedge 31 extends in the length of the evacuation channel. 27. Thus, it is possible to adjust the section of the evacuation channel to prevent penetration of raw gum into this channel during vulcanization, while allowing an evacuation of the air out of the mold. The clogging wedge 31 may have different thicknesses depending on the composition of the raw gum used. Note also that the blocking wedge 31 may be formed of the same material as the molding element and it is attached to this molding element by gluing, screwing or any other means.

[52] In an alternative embodiment not shown, it is possible that the shim 25 of Figure 3 and the blocking wedge 31 of Figure 5 form a single piece. [53] Figure 6 shows a part of a mold vulcanizing a tread of a tire. This mold portion comprises a first molding member 1a and a second molding member 1b in contact with each other. These molding elements form a cavity 33 for molding a device for closing the section of a groove formed by the cord 35. More particularly, the cavity 33 is delimited by walls belonging to the first molding element 1a such that transverse wall 19a, two longitudinal walls 21a and a bottom wall not visible here. The cavity 33 is also delimited by a contact surface 17b belonging to the second molding element 1b. It will be noted that the width of the cavity 33 is between 0.1 mm and 2 mm.

[54] Figure 7 shows an alternative embodiment in which the cavity

33 of the mold is formed by two recesses 15a and 15b each belonging to two different molding elements la and lb.

[55] Figure 8 shows an alternative embodiment of a molding element

1 having two recesses 37, 39. Each of these recesses opens on the upper face 9 of the cord 5 and on the contact edge 17 of the molding element. None of these recesses emerge on the longitudinal faces 1 1 of the cord. Thus, by virtue of the molding element of FIG. 8, it is possible to mold two closure devices in the same groove, each of these closure devices being able to close off part of the cross section of this groove. Note that the two recesses 37, 39 may have different dimensions.

[56] Figure 9 shows another alternative embodiment of a molding element 1. In this embodiment, the recess opens on the contact edge 17 through an opening 41 which is completely defined by the molding element 1 and this recess opens on the upper face 9 by an orifice 43 entirely delimited by this upper face 9. In this way, it is possible to manufacture a closure device having at its base a lower thickness than the rest of the device. This improves the overall flexibility of the closure device.

[57] The invention also covers tires molded by a mold formed from the assembly of molding elements as described above. These tires thus comprise closure devices in grooves. It should be noted that the use of these tires can be varied (tires for passenger vehicles, tires for heavy goods vehicles, for winter driving, on wet roads, etc.).

[58] The invention is not limited to the examples described and shown and various modifications can be made without departing from its scope.

Claims

1. molding element for a mold for vulcanizing a tread of a tire, said molding element (1) comprising a base (3) capable of molding a portion of the tread surface of the tread and a cord (5) adapted to mold a groove in the tread, said cord comprising two longitudinal faces (11) extending in the length of the cord protruding from said base and an upper face (9) connecting said faces longitudinal, said molding element having a contact edge (17) formed by the base and the cord, said contact edge being intended to come into contact with another molding element to form all or part of the vulcanization mold characterized in that said molding element comprises at least one recess (15) in the cord, said recess opening on the upper face (9) of the cord and on the contact edge (17) of the molding element, said renfoncem ent does not lead to the longitudinal faces (11) of this cord.

2. A molding element according to claim 1, characterized in that said molding element comprises in the cord a first recess (37) and a second recess (39), each of these recesses opening on the upper face (9) of the cord and on the contact edge of the molding element (17), none of these recesses opening on the longitudinal faces (11) of this cord.

3. A molding element according to any one of claims 1 or 2, characterized in that said molding element comprises an air outlet channel (27), said evacuation channel extending the recess or each recess in all the thickness of the base (3).

4. A molding element according to claim 3, characterized in that said molding element comprises means (31) for adjusting the dimensions of the evacuation channel. air.

5. A molding element according to any one of claims 1 to 4, characterized in that said molding element comprises means (25) for adjusting the height of the recess or each recess in the bead.

6. Mold for vulcanizing a tread of a tire comprising a plurality of molding elements (la, lb), said molding elements being in contact with each other to form a molding surface capable of molding a running surface of the tread of the tire and at least one bead (35) capable of molding a groove in the tread, said bead having two longitudinal faces extending in the length of the bead protruding from the molding surface and an upper face connecting said longitudinal faces, characterized in that said mold comprises at least one cavity (33) capable of molding a closure device intended to close all or part of a cross section of the groove molded by the cord, said cavity opening on the upper face of the cord and not opening on the longitudinal sides of the cord so that the closure device molded by the cavity came from my only with the bottom of the groove and in that the cavity is delimited by walls (19a, 21a, 17b) belonging to two molding elements (1a, 1b) in contact with each other and at least one of said molding elements is according to any one of claims 1 to 5.

7. vulcanization mold according to claim 6 characterized in that the cavity (33) is formed by two recesses (15a, 15b) vis-à-vis, each recess belonging respectively to one of the two molding elements in contact with each other; against each other.

8. vulcanization mold according to claim 6 characterized in that the cavity (33) comprises a single recess belonging to one of the two molding elements, said cavity being formed by said recess and by a contact edge (17b) belonging to the another molding element, said contact edge closing said recess.

9. vulcanization mold according to any one of claims 6 to 8 characterized in that the width of the cavity is between 0.1 mm and 2 mm.

A tire tread molded and vulcanized from a vulcanization mold according to any one of claims 6 to 9.